Functionally Strain-Graded Nanoscoops for High Power Li-Ion Battery Anodes

Lithium ion batteries show poor performance for high power applications involving ultrafast charging/discharging rates. Here we report a functionally strain graded carbon-aluminum-silicon anode architecture that overcomes this drawback. It consists of an array of nanostructures each comprising an amorphous carbon nanorod with an intermediate layer of aluminum that is finally capped by a silicon nanoscoop on the very top. The gradation in strain arises from graded levels of volumetric expansion in these three materials on alloying with lithium. The introduction of aluminum as an intermediate layer enables the gradual transition of strain from carbon to silicon, thereby minimizing the mismatch at interfaces between differentially strained materials and enabling stable operation of the electrode under high-rate charge/discharge conditions. At an accelerated current density of similar to 51.2 A/g (i.e., charge/discharge rate of similar to 40C), the strain-graded carbon-aluminum-silicon nanoscoop anode provides average capacities of similar to 412 mAh/g with a power output of similar to 100 kW/kg(electrode) continuously over 100 charge/discharge cycles.